Initial power up or power outage refrigerant purge

ABSTRACT

A method for diluting a leaked refrigerant in a refrigeration system according to an example of the present disclosure includes operating the refrigeration system in a purge mode based on at least one purge condition prior to initiating a compressor of the refrigeration system. A refrigeration system according to an example of the present disclosure includes a compressor configured to compress refrigerant in a refrigerant line, a heat exchanger configured to exchange heat with the refrigerant line in a heat exchange mode, a fan configured to pass air through the heat exchanger to an indoor space, and a controller configured to operate the refrigeration system in a purge mode based on at least one purge condition prior to initiating the compressor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/899,387, filed Sep. 12, 2019, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to a refrigeration system, and more particularly to a method of dissipating refrigerant leaked from a refrigeration system.

Buildings, such as commercial buildings including university buildings, office buildings, hospitals, restaurants and residential buildings such as single family, multi-family and high rise residential and the like, include refrigeration systems which are operable to control the climate inside the building. A typical refrigeration system includes an evaporator, indoor fan, one or more compressors, a condenser, and an expansion valve. This system and components utilize circulating refrigerant to maintain an indoor temperature of the building at a desired level.

Traditionally, refrigeration systems have used A1 refrigerants as defined by standards like ASHRAE 34, which are non-flammable. However, global warming and other environmental concerns have caused the heating, ventilation, and air conditioning (HVAC) industry to explore alternative lower Global Warming Potential (GWP) refrigerants, such as A2L refrigerants, in place of existing A1 refrigerants in HVAC systems. Although these alternative refrigerants have a lower GWP, they are often mildly flammable.

SUMMARY

A method for diluting a leaked refrigerant in a refrigeration system according to an example of the present disclosure includes operating the refrigeration system in a purge mode based on at least one purge condition prior to initiating a compressor of the refrigeration system.

In a further embodiment of any of the foregoing embodiments, operating the refrigeration system in the purge mode comprises operating a fan to pass air through a heat exchanger of the refrigeration system.

In a further embodiment of any of the foregoing embodiments, the at least one purge condition includes a detected power outage to the compressor.

In a further embodiment of any of the foregoing embodiments, the at least one purge condition includes the compressor and fan being off for at least a predefined time period.

In a further embodiment of any of the foregoing embodiments, operating the fan includes operating the fan for a predefined time period sufficient to dissipate refrigerant leaked from the heat exchanger into an air duct and a building, and reduce a concentration of the leaked refrigerant below a predefined level.

In a further embodiment of any of the foregoing embodiments, a calibration adjustment of a refrigerant sensor associated with the heat exchanger is performed prior to initiating the compressor and after the fan has operated for the predefined time period during the purge mode. The calibration adjustment includes determining a new sensor reading to utilize as a baseline for non-detection of leaked refrigerant in the refrigeration system.

In a further embodiment of any of the foregoing embodiments, performing the calibration adjustment includes determining a previous sensor reading utilized as a baseline for non-detection of leaked refrigerant in the refrigeration system, and triggering an alarm if a magnitude of a difference between the new and previous sensor readings exceeds a predefined alert threshold.

In a further embodiment of any of the foregoing embodiments, the refrigerant sensor is disposed within the heat exchanger.

In a further embodiment of any of the foregoing embodiments, during a heat exchange mode at least one of the compressor and an auxiliary heating device is also operated that heats air exiting or entering the heat exchanger. During the purge mode, the compressor and auxiliary heating device are maintained in an off state. The auxiliary heating device includes an electric or gas heater.

In a further embodiment of any of the foregoing embodiments, during a heat exchange mode, the compressor is operated and an air cleansing device that cleanses air exiting or entering the heat exchanger is also operated. During the purge mode, the compressor and air cleansing device are maintained in an off state. The air cleansing device includes an electrostatic air cleaner or a short-wavelength ultraviolet (UVC) light.

A refrigeration system according to an example of the present disclosure includes a compressor configured to compress refrigerant in a refrigerant line, a heat exchanger configured to exchange heat with the refrigerant line in a heat exchange mode, a fan configured to pass air through the heat exchanger to an indoor space, and a controller configured to operate the refrigeration system in a purge mode based on at least one purge condition prior to initiating the compressor.

In a further embodiment of any of the foregoing embodiments, to operate the refrigeration system in the purge mode, the controller is configured to operate the fan to pass air through the heat exchanger.

In a further embodiment of any of the foregoing embodiments, the at least one purge condition includes a detected power outage to the compressor.

In a further embodiment of any of the foregoing embodiments, the at least one purge condition includes the compressor and fan being off for at least a predefined time period.

In a further embodiment of any of the foregoing embodiments, the controller is configured to operate the fan during the purge mode for a predefined time period sufficient to dissipate refrigerant leaked from the heat exchanger into an air duct and building, and reduce a concentration of the leaked refrigerant below a predefined level.

In a further embodiment of any of the foregoing embodiments, a refrigerant sensor is configured to detect leaked refrigerant in the refrigeration system, and the controller is configured to perform a calibration adjustment of the refrigerant sensor prior to initiating the compressor and after the fan has operated for the predefined time period during the purge mode. As part of the calibration adjustment, the controller is configured to determine a new sensor reading to utilize as a baseline for non-detection of leaked refrigerant in the refrigeration system.

In a further embodiment of any of the foregoing embodiments, as part of the calibration adjustment, the controller is configured to determine a previous sensor reading utilized as a baseline for non-detection of leaked refrigerant in the refrigeration system, and trigger an alarm if a magnitude of a difference between the new and previous sensor readings exceeds a predefined alert threshold.

In a further embodiment of any of the foregoing embodiments, the refrigerant sensor is disposed within the heat exchanger.

In a further embodiment of any of the foregoing embodiments, an auxiliary heating device is configured to heat air exiting the heat exchanger. The auxiliary heating device includes an electric heater or a gas heater. The controller is configured to, during a heat exchange mode, operate at least one of the compressor and the auxiliary heating device, and during the purge mode, maintain the compressor and auxiliary heating device in an off state.

In a further embodiment of any of the foregoing embodiments, an air cleansing device is configured to cleanse air exiting the heat exchanger. The air cleansing device includes an electrostatic air cleaner or a short-wavelength ultraviolet (UVC) light. The controller is configured to, during a heat exchange mode, operate the compressor and also operate the air cleansing device, and during the purge mode, maintain the compressor and air cleansing device in an off state.

The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an example refrigeration system which is a cooling system.

FIG. 2 is a schematic view of an example refrigeration system that utilizes a heat pump.

FIG. 3 is a schematic view of an example heat exchanger from a residential system.

FIG. 4 is a flowchart illustrating an example method for diluting a leaked refrigerant in a refrigeration system.

FIG. 5 is a schematic view of a controller for a refrigeration system.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of an example refrigeration system 20A that includes a compressor 22A, a first heat exchanger 24A, an expansion device 26A, and a second heat exchanger 28A. Refrigerant in a suction line 29 is compressed in the compressor 22A, and exits the compressor 22A at a high pressure, high temperature, and a high enthalpy, and flows to the first heat exchanger 24A. Although only a single compressor 22A is shown, it is understood that multiple compressors could be used.

In a cooling operation, the first heat exchanger 24A operates as a condenser that rejects heat. In the first heat exchanger 24A, refrigerant flows through one or more coil tubes 30A and rejects heat to air that is drawn over the coil tube(s) 30A by a fan 32A. In the first heat exchanger 24A, refrigerant is condensed into a liquid that exits the first heat exchanger 24A at a low enthalpy and a high pressure. The heat rejection medium can be ambient air or could be water in a shell and tube arrangement, for example.

The refrigerant flows from the first heat exchanger 24A to the expansion device 26A, such as a thermostatic expansion valve or electronic expansion valve. The expansion device 26A reduces the refrigerant to a low pressure and temperature. After expansion, the refrigerant flows through the second heat exchanger 28A, which operates as an evaporator that accepts heat. A blower fan 34A (which may be a centrifugal fan) draws air through the second heat exchanger 28A and over a coil refrigerant tubes 36A. The refrigerant flowing through the coil refrigerant tubes 36A and accepts heat from air, exiting the second heat exchanger 28A at a high enthalpy and a low pressure. The refrigerant then flows to the compressor 22A, completing its refrigeration cycle. The cooling medium could be air or could be water in a shell and tube arrangement, for example.

A controller 38A controls operation of each of the compressor 22A, fan 32A, and fan 34A, and operates each of these components during a heat exchange mode when the refrigeration system 20A is running. In the heat exchange mode, the refrigeration system 20A is operated to cool and dehumidify air. In embodiments utilizing an electronic expansion valve for the expansion device 26A, the controller 38A could also control the expansion device 26A, and operate the expansion device 26A in the heat exchange mode.

FIG. 2 illustrates another type of refrigeration system, which is a heat pump 20B, capable of operating in both cooling and heating modes. The heat pump 20B includes a compressor 22B that delivers refrigerant through a discharge port 44 that is returned back to the compressor 22B through a suction port 46. Although only a single compressor 22B is shown, it is understood that multiple compressors could be used.

Refrigerant moves through a four-way valve 48 that can be switched between heating and cooling positions to direct the refrigerant flow in a desired manner (indicated by the arrows associated with valve 48 in FIG. 2) depending upon the requested mode of operation, as is well known in the art. When the valve 48 is positioned in the cooling position, refrigerant flows from the discharge port 44 through the valve 48 to an outdoor heat exchanger 24B, which includes a coil 30B, and where heat from the compressed refrigerant is rejected to a secondary fluid, such as ambient air. A fan 32B is used to provide airflow through the outdoor heat exchanger 24B.

The refrigerant flows from the outdoor heat exchanger 24B through a first fluid passage 56 into an expansion device 26B, which can be a thermostatic expansion valve or electronic expansion valve, for example. The refrigerant when flowing in this forward direction expands as it moves from the first fluid passage 56 to a second fluid passage 58, thereby reducing its pressure and temperature. The expanded refrigerant flows through an indoor heat exchanger 28B, which includes a coil 36B, to accept heat from another secondary fluid and supply cold air indoors. A fan 34B (which may be a centrifugal fan) provides air flow through the heat exchanger 28B. The refrigerant returns from the indoor exchanger 28B to the suction port 46 through the valve 48.

When the valve 48 is in the heating position, refrigerant flows from the discharge port 44 through the valve 48 to the indoor heat exchanger 28B where heat is rejected to the indoors. The refrigerant flows from the indoor heat exchanger 28B through second fluid passage 58 to the expansion device 26B. As the refrigerant flows in this reverse direction from the second fluid passage 58 through the expansion device 26B to the first fluid passage 56, the refrigerant flow is more restricted in this direction as compared to the forward direction. The refrigerant flows from the first fluid passage 56 through the outdoor heat exchanger 24B, four-way valve 48 and back to the suction port 46 through the valve 48.

A controller 38B controls operation of each of the compressor 22B, fan 32, fan 34B, and valve 48 when the heat pump 20B is operating in a heating or cooling mode. In embodiments utilizing an electronic expansion valve for the expansion device 26B, the controller 38B would also control the expansion device 26B while the heat pump 20B is operating in a heating or cooling mode.

The refrigeration system 20 can be used in a number of applications, such as in residential split systems and packaged systems and in commercial rooftop systems, indoor packaged systems and split systems. When used with a residential and commercial split system, the heat exchanger 28 is located inside a residence and the fan 34 draws air through the evaporator 28. Also, when used in the residential system, the heat exchanger 24 is located outside the residence.

When used with a rooftop system and packaged units, the refrigeration system 20 is located on a rooftop or an exterior of a building. In this configuration, the refrigeration system 20 includes an evaporator section that draws air from inside the building and conditions it with the heat exchanger 28 and directs the air back into the building. Additionally, the refrigeration system 20 for the rooftop application would include an outdoor section with the fan 32 drawing ambient air through the heat exchanger 24 to remove heat from the heat exchanger 24 as described above.

FIG. 3 is a schematic view of an example HVAC unit 60 that could be used as either of the heat exchangers 28A-B. The HVAC unit 60 receives air from a return air duct 62 and provides air to a supply duct 64, and when the refrigeration system is operating in the heat exchange mode, that air is thermally conditioned. Refrigerant passes through a coil 66 in the HVAC unit 60. A blower fan 68 (which may be used as fan 34) draws air over the coil 66 to exchange heat with the coil 66. One or more air cleaning devices 70 are provided at an inlet of the HVAC unit 60. The air cleansing device(s) could include an electrostatic air cleaner or a short-wavelength ultraviolet (UVC) light, for example.

One or more auxiliary heating devices 72 are provided at an outlet of the HVAC unit 60 to provide auxiliary heating during the heat exchange mode. The auxiliary heating device(s) could include an electric or gas heater, for example.

A refrigerant sensor 74 is provided in proximity to the coil 66 for detecting leaked refrigerant. The refrigerant sensor 74 could be a non-dispersive infrared (NDIR) sensor, metal oxide (MOS) sensor, or optical sensor. During operation of a refrigeration system in the heat exchange mode (which could be a cooling mode of refrigeration system 20A or 20B, or a heating mode of refrigeration system 20B), the blower fan 68 would be operating. However, when the refrigeration system 20 is not operating, there is a greater potential for leaking refrigerant to accumulate inside the HVAC unit 60. Using A2L refrigerants as an example, the refrigerants are not flammable until they reach a threshold level of concentration in a given volume (e.g., a concentration on the order of 14%).

To reduce the likelihood of ignition of leaked refrigerant, the controller 38 includes a purge mode in which the fan 68 is operated prior to turning on other components of the refrigeration system 20 in the heat exchange mode, such as the compressor 22, air cleansing device(s) 70, and/or auxiliary heating device(s) 72. The purge mode prevents such components from providing heat and/or an electrical arc that could ignite leaked refrigerant. The purge mode also dissipates refrigerant that may have leaked from either of the heat exchangers 24, 28.

FIG. 4 is a flowchart 100 illustrating an example method for diluting a leaked refrigerant in a refrigeration system 20. The controller 38 monitors a status of the compressor 22 (step 102), and checks if the compressor 22 is off for a first predefined time period or is off due to a power outage (step 104). If neither of the criteria of step 104 are met (a “no” to step 104), the controller 38 continues monitoring the status of the compressor (step 102). Otherwise, if either of the criteria of step 104 are met (a “yes” to step 104), the controller 38 initiates the purge mode by turning off and/or maintaining each of the compressor 22, air cleansing device(s) 70, and auxiliary heating device(s) 72 in an off state, and operating the fan 68 to pass air through the HVAC unit 60 of the refrigeration system 20 for a second predefined time period (step 106). Operation of the fan 68 (e.g., an indoor fan such as fan 34A) circulates air through the ductwork and building associated with the refrigeration system 20, thereby dispersing refrigerant leaked from the heat exchange over a greater area (e.g., into ductwork and a building that houses the ductwork) to dilute the refrigerant below a predefined concentration level (e.g., a flammable concentration level).

In one embodiment, the first predefined time period of compressor 22 off time that triggers the purge mode is approximately 24 hours. In an embodiment, the second predefined time period during which the fan 68 is run during the purge mode may be selected to have a duration sufficient to dissipate leaked refrigerant that has collected in the HVAC unit 60 through the supply duct 64. In one embodiment, the duration is approximately 5 minutes. iated that the duration may be greater than or less than 5 minutes. Of course, other first and second time periods could be used.

After the fan 68 has operated for the duration of the second predefined time period, the controller 38 performs a calibration adjustment of the refrigerant sensor 74 prior to initiating the heat exchanging mode (step 108). The calibration adjustment includes the controller 38 determining a new sensor reading of the refrigerant sensor 74 to utilize as a baseline for non-detection of leaked refrigerant in the refrigeration system 20, as leaked refrigerant should have been purged from the HVAC unit 60 from the purge mode. The determination of the new baseline value can serve as a “zero point calibration.” In one example, the calibration adjustment of step 108 is performed prior to initiating the compressor 22 and other potential ignition sources (e.g., air cleansing device(s) 70 and/or auxiliary heating device(s) 72).

In one example, the calibration adjustment of step 108 also includes the controller 38 determining a previous sensor reading of the refrigerant sensor 74 that was previously utilized as a baseline for non-detection of leaked refrigerant in the refrigeration system, and triggering an alarm if a magnitude of a difference between the new and previous sensor readings exceeds a predefined alert threshold, as this could indicate that there is a faulty sensor. A difference that exceeds the alert threshold could be indicative of a failure or impending failure of the refrigerant sensor 74, for example.

FIG. 5 is a schematic view of a controller 200 that can be used as the controller 38. The controller 200 includes a processor 202 that is operatively connected to memory 204 and a communication interface 206. The processor 202 may include one or more microprocessors, microcontrollers, application specific integrated circuits (ASICs), or the like, for example.

The memory 204 can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). Moreover, the memory 204 may incorporate electronic, magnetic, optical, and/or other types of storage media. The memory 204 can also have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor 202.

The communication interface 206 is configured to facilitate communication between the controller 200 and some or all of the compressor 22, expansion device 26 (if it is an electronic device), fans 32 and 34, air cleansing device(s) 70, auxiliary heating device(s) 72, and refrigerant sensor 74. In one example, multiple controllers 200 are included (e.g., one controller for general operation of the refrigeration system 20 in the heat exchanging mode, and one controller for performing the method 100). In one example, the communication interface 206 includes a wireless interface for wireless communication and/or a wired interface for wired communications.

Although example embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure. 

What is claimed is:
 1. A method for diluting a leaked refrigerant in a refrigeration system, comprising: operating the refrigeration system in a purge mode based on at least one purge condition prior to initiating a compressor of the refrigeration system.
 2. The method of claim 1, operating the refrigeration system in the purge mode comprises operating a fan to pass air through a heat exchanger of the refrigeration system.
 3. The method of claim 2, wherein the at least one purge condition comprises a detected power outage to the compressor.
 4. The method of claim 2, wherein the at least one purge condition comprises the compressor and fan being off for at least a predefined time period.
 5. The method of claim 2, wherein said operating the fan comprises operating the fan for a predefined time period sufficient to dissipate refrigerant leaked from the heat exchanger into an air duct and a building, and reduce a concentration of the leaked refrigerant below a predefined level.
 6. The method of claim 5, comprising: performing a calibration adjustment of a refrigerant sensor associated with the heat exchanger prior to initiating the compressor and after the fan has operated for the predefined time period during the purge mode, wherein the calibration adjustment comprises determining a new sensor reading to utilize as a baseline for non-detection of leaked refrigerant in the refrigeration system.
 7. The method of claim 6, wherein said performing the calibration adjustment comprises: determining a previous sensor reading utilized as a baseline for non-detection of leaked refrigerant in the refrigeration system; and triggering an alarm if a magnitude of a difference between the new and previous sensor readings exceeds a predefined alert threshold.
 8. The method of claim 6, wherein the refrigerant sensor is disposed within the heat exchanger.
 9. The method of claim 1, comprising: during a heat exchange mode, operating at least one of the compressor and an auxiliary heating device that heats air exiting or entering the heat exchanger; and during the purge mode, maintaining the compressor and auxiliary heating device in an off state; wherein the auxiliary heating device comprises an electric or gas heater.
 10. The method of claim 1, comprising: during a heat exchange mode, operating the compressor and also operating an air cleansing device to cleanse air exiting or entering the heat exchanger; and during the purge mode, maintaining the compressor and air cleansing device in an off state; wherein the air cleansing device comprises an electrostatic air cleaner or a short-wavelength ultraviolet (UVC) light.
 11. A refrigeration system comprising: a compressor configured to compress refrigerant in a refrigerant line; a heat exchanger configured to exchange heat with the refrigerant line in a heat exchange mode; a fan configured to pass air through the heat exchanger to an indoor space; and a controller configured to operate the refrigeration system in a purge mode based on at least one purge condition prior to initiating the compressor.
 12. The refrigeration system of claim 11, wherein to operate the refrigeration system in the purge mode, the controller is configured to operate the fan to pass air through the heat exchanger.
 13. The refrigeration system of claim 12, wherein the at least one purge condition comprises a detected power outage to the compressor.
 14. The refrigeration system of claim 12, wherein the at least one purge condition comprises the compressor and fan being off for at least a predefined time period.
 15. The refrigeration system of claim 12, wherein the controller is configured to operate the fan during the purge mode for a predefined time period sufficient to dissipate refrigerant leaked from the heat exchanger into an air duct and a building, and reduce a concentration of the leaked refrigerant below a predefined level.
 16. The refrigeration system of claim 15, comprising: a refrigerant sensor configured to detect leaked refrigerant in the heat exchanger; wherein the controller is configured to perform a calibration adjustment of the refrigerant sensor prior to initiating the compressor and after the fan has operated for the predefined time period during the purge mode, wherein as part of the calibration adjustment, the controller is configured to determine a new sensor reading to utilize as a baseline for non-detection of leaked refrigerant in the heat exchanger.
 17. The refrigeration system of claim 16, wherein as part of the calibration adjustment, the controller is configured to: determine a previous sensor reading utilized as a baseline for non-detection of leaked refrigerant in the heat exchanger; and trigger an alarm if a magnitude of a difference between the new and previous sensor readings exceeds a predefined alert threshold.
 18. The refrigeration system of claim 16, wherein the refrigerant sensor is disposed within the heat exchanger.
 19. The refrigeration system of claim 11, comprising: an auxiliary heating device configured to heat air exiting the heat exchanger, wherein the auxiliary heating device comprises an electric heater or a gas heater; wherein the controller is configured to: during a heat exchange mode, operate at least one of the compressor and the auxiliary heating device; and during the purge mode, maintain the compressor and auxiliary heating device in an off state.
 20. The refrigeration system of claim 11, comprising: an air cleansing device configured to cleanse air exiting the heat exchanger, wherein the air cleansing device comprises an electrostatic air cleaner or a short-wavelength ultraviolet (UVC) light; and wherein the controller is configured to: during a heat exchange mode, operate the compressor and also operate the air cleansing device; and during the purge mode, maintain the compressor and air cleansing device in an off state. 